Carnegie Releases CETO 5 Unit Design (Australia)

Wave energy developer, Carnegie Wave Energy Limited to release the design of its CETO 5 unit which will be used in the Perth Wave Energy Project (PWEP) at Garden Island in Western Australia.

The CETO 5 design builds on the experience gained in previous generations and incorporates some important improvements. The diameter of the buoyant actuator has the most significant influence on power output and has been increased to 11m from the 7m diameter CETO 3 unit successfully tested at the Garden Island site in 2011.

Further optimisation of the design and tuning of the hydraulics has been undertaken which, together with the increase in buoyant actuator diameter, leads to a rated capacity of approximately 240 kW. This capacity is some three times that of the CETO 3 unit that was tested at the Garden Island site in 2011 and higher again than the 10m CETO 4 unit currently being deployed by EDF and DCNS off Reunion Island.

Performance in lower wave energy conditions has also been improved meaning that power is produced at a high wave energy site such as those along the southern Australian coastline for more than 97% of the time.

As with the in-ocean operation of previous CETO units, all critical performance variables will be validated during the project through the use of specialised in-ocean measurement and communications equipment. In total over 200 sensors will provide essential data which is used to validate hydrodynamic, kinematic and hydraulic computational models. These models form part of the core intellectual property of Carnegie and are used for forecasting output for both current and future designs at the potential project sites.

The CETO 5 design has been under development for over 12 months. The highly complex hydrodynamics of the buoyant actuator is calculated using a combination of leading industry software and Carnegie’s own customised codes. These calculations deliver the mechanical output of the buoyant actuator which corresponds to the forces and motions applied to the pump. These forces are manifested as hydraulic pressures and flows which together form the critical engineering values in the design of the unit components. For the CETO 5 design, instantaneous energies in excess of 1 MW must be managed by the unit.

The key system input is the wave resource and Carnegie’s own wave monitoring buoy, deployed at the Garden Island site since 2009, provides the most accurate wave data possible. These data sets are analysed and refined for use in Carnegie’s computational models. When combined, these models simulate the entire CETO wave energy plant where all parameters can be adjusted and scenarios tested.

Each CETO unit is attached to a pile and grouted foundation similar to that used for CETO 3 except CETO 5 utilises oil and gas standard “quick connect” technology that will reduce unit installation time by 80% over previous CETO generations. Each unit in turn connects to the pipeline via a manifold located central to the array. Simulations for this equipment study pressure fluctuations including transient effects due to fluid inertia.

This tool also optimises pipe dimension to balance hydraulic losses and pipe costs.

Onshore, the generation equipment is modelled and simulations test the control algorithms that optimise conversion efficiency of hydraulic energy to electrical energy.

Design of the controller also incorporates management of the significant quantities of data being generated, currently estimated at more than 1GB per day.

This design process, the corresponding calculations and the design itself will be independently reviewed at the end of the detailed design phase which incorporates the entire CETO system for the Perth Wave Energy Project. This phase is on track for completion at the end of 2012.